Gupta Sanju, Evans Brendan, Henson Alex, Carrizosa Sara B
Department of Physics and Astronomy and Biotechnology Center, Western Kentucky University, Bowling Green, KY 42101, USA.
Department of Chemistry, Western Kentucky University, Bowling Green, KY 42101, USA.
Materials (Basel). 2017 Nov 10;10(11):1292. doi: 10.3390/ma10111292.
Nanodiamond particles form agglomerates in the dry powder state and this poses limitation to the accessibility of their diamond-like core thus dramatically impacting their technological advancement. In this work, we report de-agglomeration of nanodiamond (ND) by using a facile technique namely, salt-assisted ultrasonic de-agglomeration (SAUD). Utilizing ultrasound energy and ionic salts (sodium chloride and sodium acetate), SAUD is expected to break apart thermally treated nanodiamond aggregates (~50-100 nm) and produce an aqueous slurry of de-aggregated stable colloidal nanodiamond dispersions by virtue of ionic interactions and electrostatic stabilization. Moreover, the SAUD technique neither has toxic chemicals nor is it difficult to remove impurities and therefore the isolated nanodiamonds produced are exceptionally suited for engineered nanocarbon for mechanical (composites, lubricants) and biomedical (bio-labeling, biosensing, bioimaging, theranostic) applications. We characterized the microscopic structure using complementary techniques including transmission electron microscopy combined with selected-area electron diffraction, optical and vibrational spectroscopy. We immobilized SAUD produced NDs on boron-doped diamond electrodes to investigate fundamental electrochemical properties. They included surface potential (or Fermi energy level), carrier density and mapping electrochemical (re)activity using advanced scanning electrochemical microscopy in the presence of a redox-active probe, with the aim of understanding the surface redox chemistry and the interfacial process of isolated nanodiamond particles as opposed to aggregated and untreated nanoparticles. The experimental findings are discussed in terms of stable colloids, quantum confinement and predominantly surface effects, defect sites (sp²-bonded C and unsaturated bonds), inner core (sp³-bonded C)/outer shell (sp²-bonded C) structure, and surface functionality. Moreover, the surface electronic states give rise to midgap states which serve as electron donors (or acceptors) depending upon the bonding (or antibonding). These are important as electroanalytical platforms for various electrocatalytic processes.
纳米金刚石颗粒在干粉状态下会形成团聚体，这限制了其类金刚石核心的可及性，从而极大地影响了它们的技术进步。在这项工作中，我们报道了通过一种简便的技术——盐辅助超声解聚（SAUD）来实现纳米金刚石（ND）的解聚。利用超声能量和离子盐（氯化钠和醋酸钠），SAUD有望使经过热处理的纳米金刚石聚集体（约50 - 100纳米）分解，并通过离子相互作用和静电稳定作用产生解聚的稳定胶体纳米金刚石分散体的水基浆料。此外，SAUD技术既没有有毒化学物质，去除杂质也不困难，因此所制备的分离纳米金刚石特别适用于机械（复合材料、润滑剂）和生物医学（生物标记、生物传感、生物成像、治疗诊断）应用的工程纳米碳材料。我们使用包括透射电子显微镜结合选区电子衍射、光学和振动光谱等互补技术对微观结构进行了表征。我们将SAUD制备的纳米金刚石固定在掺硼金刚石电极上，以研究其基本电化学性质。这些性质包括表面电位（或费米能级）、载流子密度，并在存在氧化还原活性探针的情况下，使用先进的扫描电化学显微镜绘制电化学（再）活性图谱，目的是了解分离的纳米金刚石颗粒与聚集和未处理的纳米颗粒相比的表面氧化还原化学和界面过程。实验结果从稳定胶体、量子限制和主要的表面效应、缺陷位点（sp²键合的C和不饱和键）、内核（sp³键合的C）/外壳（sp²键合的C）结构以及表面功能等方面进行了讨论。此外，表面电子态会产生带隙中间态，根据键合（或反键合）情况，这些态充当电子供体（或受体）。这些作为各种电催化过程的电分析平台很重要。
